Issue 48

M. L. Puppio et alii, Frattura ed Integrità Strutturale, 48 (2019) 706-739; DOI: 10.3221/IGF-ESIS.48.66

The diagonals of the (nbs) and the columns of the (es) are modelled with a linear-elastic behaviour. Fig. 21 and Fig. 22 shows the properties of the flexural and shear plastic hinge defined in Sap2000 (Version 2017).

Frame Hinge Property Data

Frame Hinge Property Data

C D E

C D E

B

B

A

A

E- D C-

E- D C-

Shear/SF

Moment/SF

B

B

Figure 21: Properties of the flexural plastic hinge. -1,4 -1,2 -1 -0,8 -0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1 1,2 1,4 -10 -8 -6 -4 -2 0 2 4 6 8 10 Rotation/SF

Figure 22: Properties of the shear plastic hinge. -1,4 -1,2 -1 -0,8 -0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1 1,2 1,4 -10 -8 -6 -4 -2 0 2 4 6 8 10 Displacement/SF

Preliminary study of links in series with Pushover Analysis In order to consider the effect of dissipation of the link systems the following parameters are significant:  number and configuration;  length (or eccentricity between mid-plane of the bracing system and side of the building);  mechanical slenderness of the link;  degree of restraint of the links. First of all, a non-linear static analysis is carried out in Sap 2000 (Version 17) on a series of links as described in Fig. 23. The parameters of the link systems are: number of links equal to 10, plastic hinge as extremity restraint. The beam that connects the extremity of the link is considered as rigid.

Figure 23: Scheme of the connection between existing buildings and new bracing systems. The geometrical parameters i and β are here represented. Sap 2000 allows the addition of a static horizontal load that can be increased up to the maximum displacement magnitude (1 m) of the control point. The main parameters chosen to perform the analyses are shown below:  Maximum total steps per stage: 200;  Maximum null steps per stage: 50;  Maximum Newton-Raphson Iterations per step: 40;  Iteration convergence tolerance (relative): 0.0001;  Model characteristic: 20 points, 10 Frames. The response of the system is analysed by varying the link length (that is the distance between the horizontal beam of the bracing system and the external side of the building), and the sections used for the link. The results are shown in Tab. 2 and Tab. 3. Tab. 2 reports the length variation of the profiles while Tab. 3 presents the cross-section variation. Non-linear static analyses are carried out varying the link length or its cross section. In case of length

721